Horchata manages to be creamy without containing any milk or cream. Creaminess, as fans of almond milk and coconut yogurt are aware, doesn’t actually require dairy, but rather the thickening effect of having large molecules of starch, protein and/or fat suspended in a background of water.
On a molecular level, horchata-making is about grinding, soaking and blending rice, almonds, seeds, chufas, etc. to encourage their fat, starch and/or protein molecules to migrate into the water you’re blending them with, and to float there as a thickened, milky-creamy mixture known as a suspension. Suspensions with especially tiny particles, like horchatas, will remain in this floating, opacified, viscous state indefinitely.